1. Field of the Invention
The invention relates to refrigeration systems, particularly those of the type used in refrigerated display cases installed in food supermarkets. In a more particular sense the invention may be classified as a defrosting system of the type in which the fluid refrigerant normally used for refrigeration purposes is utilized, in a gaseous state, for defrost purposes.
In yet a more particular sense, the invention can be appropriately classified with those in which the defrost by the gaseous refrigerant utilizes, as a primary source of the defrost fluid, saturated gaseous refrigerant ("cool gas") flowing from a receiver through the evaporators being defrosted, reversely to the direction in which the fluid refrigerant normally flows during a refrigerating cycle.
2. Description of the Prior Art
The prior art is known to include refrigeration systems, utilizing the same basic relative arrangement as the present invention, in respect to the location and operating characteristics, within the system, of condensers, compressors, receivers, and evaporators. Typical of systems of this type is that disclosed in U.S. Pat. No. 3,905,202 issued Sept. 16, 1975. By way of example, a defrost arrangement is incorporated in the disclosed, patented system that utilizes hot gas flowing from the discharge line of the compressor or series of compressors, for defrosting the evaporators conventionally incorporated in the refrigeration system.
It is also known to provide, in a refrigerating system of the general category described previously herein, an arrangement in which saturated gaseous refrigerant ("cool gas") flows from the top of a liquid receiver, to the evaporators for defrost purposes. Such an arrangement is found in U.S. Pat. No. 3,427,819 issued Feb. 18, 1969.
The use of a hot gas defrosting system is widespread. Such systems are highly efficient. It is thought by some of the industry, however, that hot gas defrost systems may possess some disadvantages. For example, it has been contended that hot gas defrost systems will at times cause breakage and leaks in refrigerant lines due to excessively rapid, thermal expansion of tubing embodied in the system. And, it has also been contended that the evaporator coils are subjected, in hot gas defrost systems, to excessive defrosting temperatures, and have as a result produced visual fog or steam.
Accordingly, as an alternate to hot gas defrost, for use by those who have some objections to a hot gas defrost system, it has been heretofore proposed, as for example in the above-mentioned U.S. Pat. No. 3,427,819, to use, instead of hot gas, desuperheated or "saturated gas". This is known also in the industry as "cool gas", a term which will be used for purposes of convenience hereinafter, and which will be understood as meaning desuperheated or saturated gaseous refrigerant occurring in a refrigeration system of the type here under consideration.